In a forklift, a mast is supported on its front so as to be capable of tilting by a hydraulic cylinder, and a fork is supported on the mast so as to be capable of moving vertically by a hydraulic cylinder. A control device drives a pump, according to an operation of an operation lever, to supply or exhaust hydraulic pressure to or from each hydraulic cylinder, thereby being capable of allowing the fork to tilt and moving the fork vertically.
A limit load weight by which the fork can safely travel with a load is set to such forklift. Therefore, the forklift is configured such that, when hydraulic pressure supplied from the pump exceeds a predetermined limit pressure, the hydraulic pressure cannot be supplied to each hydraulic cylinder, but to return to a tank by a relief valve.
One example of a forklift provided with an overload preventing device is described in Patent Literature 1. The overload preventing device described in the Patent Literature 1 has a supply line for introducing working fluid ejected from a pump to a cylinder tube, an outlet line for sending the working fluid from the cylinder tube, and a pressure control valve arranged in the middle of a supply line and that connects a drain to a tank, wherein the pressure control valve is used as a sequence valve that opens the drain by using the pressure of the outlet line as a pilot pressure.